The present invention generally relates to heat management systems for high power electronics equipment, and more particularly to a thermal bus system for a cabinet housing high power, high thermal profile electronic components and systems.
In many electronic systems, the efficient cooling of electronic components has become a significant problem. With the advent of large-scale integrated circuit (IC) modules containing many thousands of circuit elements, it has become possible to pack great numbers of electronic components together within a very small volume. As is well known, these integrated circuit modules generate significant amounts of heat during the course of their normal operation. Since most solid state devices are sensitive to excessive temperatures, a solution to the problem of the generation of heat by large scale IC""s in close proximity to one another has become of increasing concern to industry.
A typical prior art approach to cooling electronic components is to direct a stream of cooling air across the modules and/or circuit cards carrying such devices. However, the increasing power density of electronic systems is reaching the point where it is no longer possible to adequately cool heat generating electronic components by forcing air over them. Power densities are anticipated to reach the point where it is physically impossible to force sufficient ambient temperature air through a cabinet to adequately cool the electronics inside. Several other disadvantages to this approach have also been identified, including: high pressure drop; uniformity of component form factors; placing the components containing the integrated circuits further apart on the circuit cards; increasing the distance between circuit cards; and increasing the volume and velocity of cooling air directed over the components. This required increase in volume and velocity of cooling air requires special considerations in the design of the housings containing the circuit cards and in the mechanical systems for delivering the cooling air. Also, the air quality (moisture content, contamination, etc.) must be tightly controlled to inhibit corrosion, loss of cooling effectiveness, etc. Thus, cooling of components by this means necessitates a number of compromises to the overall system that prevent its use in many systems.
The foregoing thermal management problems have brought about the evolution of other techniques for cooling card-mounted electronic components. For example, one technique includes the use of solid metal thermal mounting cards or plates which conduct the heat dissipated by electronic components to a heat sink (cold plate) disposed at the edge of each circuit card. Such an approach, however, results in a large thermal resistance from the component mounting surface to the heat sink, which causes high component temperatures.
Other known techniques for cooling electronic systems include loop thermosyphons and heat pipes. Loop thermosyphons are devices that use gravity to maintain two-phase fluid circulation during operation. Each loop thermosyphon has an evaporator, where vaporization occurs when it is heated, a vapor tube through which the vapor flows to a condenser where it is cooled and condenses, and a liquid return tube to return the liquid to the evaporator. Sometimes a capillary structure is used in the evaporator to reduce its thermal resistance.
A heat pipe includes a sealed envelope that defines an internal chamber containing a capillary wick and a working fluid capable of having both a liquid phase and a vapor phase within a desired range of operating temperatures. When one portion of the chamber is exposed to relatively high temperature it functions as an evaporator section. The working fluid is vaporized in the evaporator section causing a slight pressure increase forcing the vapor to a relatively lower temperature section of the chamber (a condenser section). The vapor is condensed in the condenser section and returns through the capillary wick to the evaporator section by capillary pumping action. Because a heat pipe operates on the principle of phase changes rather than on the principles of conduction or convection, a heat pipe is theoretically capable of transferring heat at a much higher rate than conventional heat transfer systems. Consequently, heat pipes have been utilized to cool various types of high heat-producing apparatus, such as electronic equipment (See, e.g., U.S. Pat. Nos. 5,884,693, 5,890,371, and 6,076,595).
U.S. Pat. No. 4,366,526, issued to Lijol et al., discloses a circuit card for high-density packaging of electronic components for use in high power-density card racks in computer and other electronic and avionic systems. The card has an all metal construction with an elongate planar body for the mounting of electronic components on opposite sides, and has a heat pipe located along the edges of one elongate side and two ends. Edge tabs on the ends of the card permit the card to be installed into a card rack in electronic equipment. The elongate portion of the heat pipe serves as the evaporator section and the two end portions act as the condensing sections.
U.S. Pat. No. 4,931,905, issued to Cirrito et al., discloses two metal plates that have U-shaped grooves so that the plates may form congruent halves wherein matching grooves complete independent heat pipes. A bight section of each heat pipe serves as an evaporator section while the parallel arms of each heat pipe form condenser sections. A wick is positioned within each heat pipe to improve liquid transport when a module is in a non-upright position. The condenser sections are located coincident with the normally upright edges of each module so that, when the module is upright, the vertically disposed condenser sections of the heat pipe provide gravity-assisted liquid transport to the evaporator section.
U.S. Pat. No. 5,283,715, issued to Carlsten et al., discloses a heat pipe structure that is incorporated directly into the metal base plate of a circuit card thereby eliminating thermal contact resistance between the base plate and the heat pipe assembly. Components are mounted on a copper circuit layer bonded to a dielectric layer in a first portion of the base plate with a second portion of the base plate/heat pipe assembly extending into a heat sink/cold plate condensing area for removal of heat generated in the component portion.
U.S. Pat. No. 6,055,157, issued to Bartilson, discloses a computer module that includes a first heat pipe assembly having an evaporator plate with an evaporator surface. The first heat pipe also has a condenser in fluid communication with the evaporator plate. The evaporator plate is positioned adjacent a printed circuit board populated with at least one electronic component. When a printed circuit board having components on two sides is used, a second heat pipe having the same construction is positioned adjacent the other side of the printed circuit board so that the electronic components on the other side are positioned adjacent the evaporator surface of the second heat pipe. The evaporator plate of each heat pipe is connected to the condenser by a plurality of necked-down regions. This forms at least one window between the condenser and the evaporator plate of each heat pipe. When more than one heat pipe is used in the computing module, the windows of the various heat pipes align.
U.S. Pat. No. 6,388,882, issued to Hoover, et al., discloses a thermal energy management architecture for a functioning system of electronic components and subsystems comprising a hierarchical scheme. Here the thermal management components are operatively engaged with individual portions of the system of electronic components and subsystems, in multiple defined levels, and are substantially only thermally driven, i.e., heat transfer devices that have no moving parts and require no external power for their operations.
U.S. Pat. No. 6,536,510, issued to Khrustalev, et al., discloses a thermal bus for cabinets housing high power electronics equipment that includes two spaced-apart horizontally oriented parallel evaporators interconnected in flow communication with a condenser. Each evaporator is mounted in a support having a central recess and each having a tube having a capillary wick disposed on an internal surface and being mounted within the central recess of the support. Each of the tubes includes a closed distal end and a closed proximal end with a liquid-working fluid entrance port located at the closed proximal end of the first tube and a vaporous-working fluid exit port located at the closed proximal end of the second tube. A duct defining a central passageway and having a capillary wick disposed on the walls of the central passageway is disposed in fluid communication with the first tube and the second tube. The condenser has a vaporous-working fluid entrance port disposed in flow communication with the vaporous-working fluid exit port of the evaporator and a liquid-working fluid exit port disposed in flow communication with the liquid-working fluid entrance port of the evaporator so that a working fluid cycles; (i) through the two spaced-apart parallel evaporators, and (ii) between the condenser and the two tubes.
The present invention provides a thermal management system that passively collects waste heat from individual or groups of components and passively transports that heat to a more advantageous location where it can physically be removed by forced air, or to a location inside or outside a cabinet housing the electronic systems, where it can be transferred to an external cooling circuit or sink that may be a significant distance from the electronic system. The thermal management system of the present invention employs heat pipes and other means to collect heat from components on a circuit card and transport that heat to a thermal connector located on a card shell. The thermal management system provides a mating thermal connector which is mounted within a cabinet or chassis, and provides the means to transport heat from the circuit card to a location where it can be removed. The location may be an area within the cabinet where a sufficiently large heat sink can transfer the heat to circulated air, or may be external to the cabinet where heat can be removed by circulating liquid loops or HVAC chiller circuits.
The present invention provides a thermal bus junction arranged within an electronics system for transporting thermal energy in a directed manner from one location to another location by positioning a cold plate, having a portion of at least one heat pipe embedded within a first thermal interface surface of it, adjacent to an evaporator portion of a loop thermosyphon having a second thermal interface surface so that the second thermal interface surface is releasably pressed against the first thermal interface surface. A condenser of a first loop thermosyphon having a first thermal interface surface may also be arranged adjacent to an evaporator portion of a loop thermosyphon having a second thermal interface surface so that the second thermal interface surface is releasably pressed against the first thermal interface surface. Likewise, a cold plate having a portion of at least one heat pipe embedded within a first thermal interface surface and a condenser of a first loop thermosyphon having a second thermal interface surface may be arranged adjacent to an evaporator portion of a second loop thermosyphon having a third thermal interface surface that is releasably pressed against the first and second thermal interface surfaces.
In one embodiment, the present invention provides a thermal management system for an electronic device having one or more circuit cards arranged within an enclosure. A first thermal energy transfer assembly is thermally coupled between a heat generating structure located on a circuit card and a first thermal interface surface that is spaced away from the heat generating structure. A second thermal energy transfer assembly includes a second thermal interface surface which is arranged in confronting relation to the first thermal interface surface. A clamping mechanism is arranged to move the second thermal interface surface between (i) a first position that is spaced away from the first thermal interface surface, and (ii) a second position wherein the second thermal interface surface is pressed against the first thermal interface surface so as to allow the busing of thermal energy from the first thermal energy transfer assembly to the second thermal energy transfer assembly by heat transfer from the first thermal interface surface to the second thermal interface surface.
In another embodiment of the invention, a thermal management system is provided having at least one card-level cooling assembly including at least one loop thermosyphon having a first thermal interface surface disposed upon a condenser. At least a second loop thermosyphon is provided having a second thermal interface surface disposed upon a second evaporator and arranged in confronting relation to the first thermal interface surface. A clamping mechanism is arranged to move the second thermal interface surface between (i) a first position that is spaced away from the first thermal interface surface, and (ii) a second position wherein the second thermal interface surface is pressed against the first thermal interface surface so as to allow the busing of thermal energy from the at least one card-level cooling assembly to the at least a second loop thermosyphon by heat transfer from the first thermal interface surface to the second thermal interface surface.
In yet a further embodiment of the invention, a thermal management system is provided having a first thermal energy transfer assembly that is thermally coupled between a heat generating structure located on a circuit card and a first thermal interface surface that is spaced away from the heat generating structure. A second thermal energy transfer assembly is provided that is thermally coupled between a heat generating structure located on a circuit card and a second thermal interface surface that is spaced away from the heat generating structure. A third thermal energy transfer assembly having a third thermal interface surface arranged in confronting relation to the first and second thermal interface surfaces. A clamping mechanism is arranged to move the third thermal interface surface between (i) a first position that is spaced away from the first and second thermal interface surfaces, and (ii) a second position wherein the third thermal interface surface is pressed against the first and second thermal interface surfaces so as to allow the busing of thermal energy from the first and second thermal energy transfer assemblies to the third thermal energy transfer assembly by heat transfer from the first and second thermal interface surfaces to the third thermal interface surface.